Endoscopic third ventriculostomy (ETV) is replacing, in many neurosurgical centers, valve-regulated shunts as the initial treatment of obstructive hydrocephalus or at the time of shunt failure, [1] nevertheless only few authors, until now, have addressed the role of repeat ETV (re-ETV) after failure of the initial procedure. [2],[3],[4] Since the earliest experiences with ETV, obstruction of the stoma has been recognized as one of the possible reasons for failure and reopening of ostomy by repeating the procedure has been proposed as an alternative to shunt placement. [5] Obliteration of the orifice after a successful ETV is probably a natural healing process that can happen in some patients with a certain degree of subjectivity. More intriguing are, instead, patients who benefited from a primary ETV for long periods of time, underwent re-ETV but failed to improve!

In this issue of Neurology India, Mahapatra and his colleagues have presented their data on "Ostomy closure and the role of repeat endoscopic third ventriculostomy (re-ETV) in failed ETV procedures", [6] a large series of consecutive ETVs for hydrocephalus of different etiologies from a single institution. The aim of the study is to determine if a second ETV after an early or delayed failure (due to inadequate size of the ostomy or restenosis respectively) allows a durable resolution of the hydrocephalus. Overall, this group performed 296 ETVs over an eight-year period with a success rate of 72% on long-term follow-up. Fifty-one patients had early failure while 32 patients had delayed reoccurrence. The decision to attempt a re-ETV was based on the review of patients' intraoperative videos where the ostomy was deemed unsatisfactory at the first operation. Six of the 51 patients from the early failure arm of the study underwent re-ETV with an additional 50% clinical success rate. In the delayed failure group 26 patients underwent re-ETV with clinical improvement in 25 of them. The most impressive finding is definitely the 90% success rate of re-ETV in children less than two years of age. This is in contrast with some previous studies [1] but, in our opinion, is not so surprising and likely reflects the main role of the formation of new arachnoid membranes after the first ETV in infants with obstructive hydrocephalus, besides the optimal patients' selection of the surgeon. To the best of our knowledge, we do not know why infants below one or two years of age should have a higher failure rate. Probably also the definition of unsuccessful ETV, in these subjects, is too hasty considering the longer time of adaptation in infants. Some authors have described their experience with re-ETV [2],[3],[4] reporting an overall success rate ranging from 65-75% but showing worst results in patients younger than two years of age, and thus concluding that an age younger than two years at the first ETV is a significant predictor of worse results after a second ETV.

Our experience suggests that a re-ETV is at least as safe and effective as the first ETV in the setting of the ideal candidate: a patient older than two-three months of age with an obstructive hydrocephalus who has benefited from the first ETV for a period of at least a month. [7] Waiting for advances in imaging techniques to determine which subjects are best candidates for a re-ETV, this study remarks the importance of re-endoscopic examination of the floor of the third ventricle in patients in whom an ETV has failed before to decide to shunt them.